 Surtseyan eruptions can happen on land as well, and are caused by rising magma that comes into contact with an aquifer (water-bearing rock formation) at shallow levels under the volcano.The products of Surtseyan eruptions are generally oxidized palagonite basalts (though andesitic eruptions do occur, albeit rarely), and like Strombolian eruptions Surtseyan eruptions are generally continuous or otherwise rhythmic.A distinct defining feature of a Surtseyan eruption is the formation of a pyroclastic surge (or "base surge"), a ground hugging radial cloud that develops along with the eruption column.